1. Field
One or more embodiments relate to a phosphor and a white light emitting device including the same, and more particularly, to a phosphor having a wide emission peak in a visible wavelength region and a white light emitting device including the same.
2. Description of the Related Art
Commonly used illumination devices include fluorescent lamps and incandescent lamps. However, fluorescent lamps include mercury (Hg), which causes environmental problems. In addition, such illumination devices have short lifetimes and low efficiency and thus, low power saving efficiency. Therefore there remains a need for white light emitting illumination devices having improved efficiency.
White light emitting devices operate in various manners. For example, ultraviolet light emitting diodes (“UV LEDs”) are used as a light source to excite red, green and blue phosphors in order to generate white light, wherein red, green and blue are three primary colors of light. In some devices, blue LEDs are used as a light source to excite red and green phosphors in order to generate white light. In other devices, blue LEDs are used as a light source to excite a yellow phosphor in order to generate white light.
To convert UV light into white light having a high color rendering index (“CRI”), an emission spectrum of a phosphor is desirably similar to that of sunlight in a visible wavelength region of 380 to 780 nanometers (nm). To provide such an emission spectrum, three kinds of phosphors, such as a red, a green and a blue phosphor may be used, and the color temperature of the white light may be controlled by changing the ratio of the three phosphors. However, when three different phosphors are used, more factors are desirably considered and thus it is difficult to generate uniform white light using three phosphors. For example, when one or two phosphors are used, phosphor quality may be more easily controlled than when three phosphors are used. Thus, when one or two phosphors are used in a white light emitting device, the color coordinate deviations are reduced.